sedimentary

Chert / Flint

Silicon Dioxide (Microcrystalline Quartz, SiO2)

AI-generated identification · may be incorrect

Hardness of 7 on the Mohs scale, colors vary from gray, brown, white to black, waxy to vitreous luster, conchoidal fracture with no true cleavage, specific gravity of 2.60-2.65.

Identified July 30, 2026More sedimentary →

Explore Chert / Flint in the encyclopedia →

Identify your own rocks.

Get a report just like this from any photo, free.

App Store Google Play

Physical properties

Hardness of 7 on the Mohs scale, colors vary from gray, brown, white to black, waxy to vitreous luster, conchoidal fracture with no true cleavage, specific gravity of 2.60-2.65.

Formation & geological history

Formed through the diagenesis of silica-rich deep-sea ooze, skeletal remains of marine organisms (like diatoms or radiolarians), or as nodular replacements in limestone and chalk during the Mesozoic and Paleozoic eras.

Uses & applications

Historically used for making stone tools, arrowheads, and fire-starting (flint and steel); currently used in abrasive products, landscaping, and sometimes decorative cabochons.

Geological facts

Because of its sharp conchoidal fracture, chert was one of the primary materials used by ancient humans for making sharp implements and weapons.

Field identification & locations

Can be identified by its distinctive conchoidal (shell-like) fracture, waxy luster, and high hardness that scratches glass easily. Commonly found embedded in limestone or as pebbles in riverbeds.